Scanning method and apparatus



Feb. 14, 1933. Q J KEO'GAN 1,897,483

SCANNING METHOD AND APPARATUS Filed Feb. 24 1930 (WM/V55. 7. KfoQAavwemtoz Fatented Feb. 1 1933 UI -FETED STATES Parser ferries CE 'L'EISJ. KEOGAN, CF NORTH AELINGTOH, NEJV JERSEY, ASSIGNOE JO JENKINSTELEVISION OOB-PORATION, F JERSEY CITY, NEW JERSEY, A CORPORATION OFDELAWARE SCANNING METHCD AND APIARATUS Application filed. February 24,1330. Serial No. 430,621.

This invention relates to electro-optical systems, and withparticularity to methods and means for scanning in television, picturetransmission, or similar systems.

The principal object of the invention is to provide a novel type ofscanner whereby Streaky efiects are eliminated, and a greater detail maybe achieved in analysis and synthesis.

A feature of the invention relates to a scanning device either of thedisc or drum type wherein the scanning elements or aper tures arearranged in a plurality of separate staggered spirals or helices.

Another feature of the invention relates to the method of scanningemploying a perforated scanner, whereby the area to be scanned isanalyzed or synthesized in alternate linear elements.

Other features and advantages not specifically enumerated will beapparent after a consideration of the following detailed descriptionsand the appended claims.

Referring to the drawing Fig 1 shows a scanning disc with the scanningelements arranged in accordance with the invention;

Fig. 2 is a schematic diagram showing how the picture field is scannedin alternate overlapping strips.

While the invention will be described as applied to a scanning device ofthe disc type, it will be understood that it can equally well be appliedto other types of scanners such as drums, mirrors, traveling bands, etc.

Referring more particularly to Fig. 1, the numeral 1 represents a disc,preferably, although not necessarily, of light metal such as aluminummounted on a shaft 2 adapted to be rotated at the requisite scanningspeed by any well known means (not shown). Disc 1 is provided with twoseries of perforations or scanning elements 3 one series being arrangedin the path of a half-turn spiral 4:, the other series being arranged inthe path of another half-turn spiral 5. The numeral 6 represents thefield of view to be scanned. In accordance with well known televisionprinciples the elements 3 are spaced apart circumferentially a distanceslightly greater than the width a of the field 6. Consequently as thedisc is rotated the elements 3 of spiral 4i trace substantially parallelpaths across the field 6. In prior art devices of this general type ithas been the practice to offset the successive perforations radiallytowards the center of the disc so that each and every perforation tracesa linear element which is adjacent to the linear elements traced by nextpreceding and next succeeding perforations. In accordance with the prsent invention the perforations inspiral 4 are displaced radially sothat they trace adjacent linear strips which overlap the strips tracedby spiral l. Thus as shown in Fig. 2 the elements 7, 8, 9, etc. of onespiral trace the linear strips a, b, 0, etc, while the elements 10, ll,12, etc. of the oth r spiral trace strips (Z, c, 7', etc. which overlapthe strips a, Z), 0, etc.

As a result of the overlapped method of scanning, the streakinessincident to the prior art method of scanning is avoided, and greatereffective detail may be achieved.

While the foregoing description relates to a scanner employed at atransmitter or analyzer, it will be understood that the invention isapplicable to receiving or synthesizing devices. Similarly the scannermay take the form or" a drum or traveling band without departing fromthe spirit and scope of the invention. Other changes and modificationswill be apparent to those familiar with the art. Thus while the scanningelements are shown in Fig. 1 as of circular shape, they may be of anyother shape such as square or other polygorial shape as shown in Fig. 2.Furthermore the scanning elements may take the form of reflectors oreven lenses adapted to illuminate or expose a field of view inpolygorial or circular elemental areas.

What is claimed is:

1. The method of scanning which comprises rotating a scanning deviceabout a fixed axis, one portion of each revolution serving to scanadjacent linear elements of an object or representation, another portionof each revolution serving to scan linear elements overlapping one-halfof each of the width of the first mentioned elements.

2. The method of scanning an area for television which comprisesanalyzing said complete area in successive adjacent but nonoverlappinglinear strips, and then resoanning said complete area in other adjacentnonoverlapping strips which overlap the first mentioned strips by onehalf of their Width.

3. The method of scanning an area for television Which comprisesscanning the complete area in successive adjacent but nonoverlappinglinear strips, and then rescanning said complete area in othernon-overlapping linear strips displaced one half of the strip Width fromthe first scanning.

In testimony whereof I have hereunto set my hand on this 19th day ofFebruary A. D.

CHARLES J. KEOGAN.

